As of yet, there is no known Klingon expression for "ice cream". You might describe popsicles as nIm taD naQ(mey) ("frozen fruit juice stick(s)") and soft ice cream as tunbogh nIm taD ("frozen milk which is soft").

There must be a word for it, because in the TAS episode "Practical Joker" the virus also affected the Klingon ship. They were heard to be furious that their food synthesizers were throwing out desserts, including ice cream sundaes (or some sort of ice cream-based dessert).